Embodiments herein generally relate to alignment of belt loops that are positioned around rollers within various devices, such as printers and, more particularly to an improved alignment method and apparatus that uses multiple sensors to account for non-uniformity in the shape of the edge of the belt.
Many belt loop systems with a longitudinally (process direction) moving belt use a servo control system with an actuator (for example a steering roll) and feedback from a belt edge sensor to control the lateral (cross process) position of the belt (edge). Most belts have edges that are not straight, e.g. they have a belt edge lateral variation (profile) as a function of longitudinally position along the belt. This belt edge profile has a basic periodicity of the length of the belt loop. The belt edge profile causes a point on the belt to not move in a straight line (tracking error). In imaging, print-making, or image transfer applications this leads to position errors of images that are generated at different process direction positions along the belt.
Some solutions include methods to create straight belt edges, but this requires a special set-up. Another solution uses a one-time set-up procedure to calibrate the edge profile. The belt is run for a few revolutions at a low tracking servo gain. In the absence of disturbances, the lower servo gain causes the belt to track better. The resulting belt edge profile is an approximation of the true edge profile only to the extent of how well the belt was tracking in the presence of disturbances during calibration.